1. Field of the Invention
The present invention relates to a technology for applying an optical intensity modulation on an image displayed on a display screen so as to generate an optical state variation that is visible in a recorded image obtained through unauthorized image-capturing of the displayed image and interferes with a viewing of the recorded image.
2. Description of the Related Art
A technology for preventing unauthorized recording of an image displayed on a display screen (image/video piracy) is disclosed in U.S. Pat. No. 6,018,374. In the related art disclosed in U.S. Pat. No. 6,018,374, difference of imaging characteristics between human vision and an image-capturing apparatus such as camera is considered, and infrared light is utilized as a means for preventing image/video piracy. Specifically, the related art employs a system in which infrared light projector is placed in a vicinity of an image projector or any other position far from the screen. In the system, infrared light is projected from an infrared light projector to the screen so that infrared light reflected at the screen can fall upon the image-capturing apparatus operated by a person conducting image/video piracy. In other words, the technology enables to record an infrared image unrelated to a feature film/video program image when image/video piracy is conducted. Accordingly, quality of the recorded image obtained through image/video piracy can be damaged, and even a location at which image/video piracy has been conducted may be identified. Of course, audience/spectator/viewer (referred as audience hereafter) directly viewing a feature film/video image can enjoy it without any difficulty since infrared light cannot be perceived by the human vision.